CN114031650B

CN114031650B - Chitosan oligosaccharide selenium coordination compound and preparation method and application thereof

Info

Publication number: CN114031650B
Application number: CN202111435680.6A
Authority: CN
Inventors: 魏新林; 张梦柯; 张亚园
Original assignee: Shanghai Jiaotong University
Current assignee: Shanghai Jiaotong University
Priority date: 2021-11-29
Filing date: 2021-11-29
Publication date: 2023-05-02
Anticipated expiration: 2041-11-29
Also published as: CN114031650A

Abstract

The invention provides a chitosan oligosaccharide selenium coordination compound and a preparation method and application thereof, wherein the preparation method comprises the following steps: dissolving chitosan oligosaccharide in water, stirring and dissolving, and ultrafiltering to obtain chitosan oligosaccharide solution; mixing the chitosan oligosaccharide solution and the glucosamine solution, and stirring until the chitosan oligosaccharide solution and the glucosamine solution are dissolved; dropping inorganic selenium solution, stirring until the reaction liquid changes from colorless to red and no change occurs; dialyzing the reaction solution, concentrating, and drying; according to the invention, by utilizing a leaf surface spraying mode, the chitosan oligosaccharide selenium coordination compound is used in the planting of tea, after the chitosan oligosaccharide selenium coordination compound is absorbed by tea leaves, the selenium content of the tea is obviously increased, and the produced selenium-enriched tea accords with the industry standard of the selenium-enriched tea; meanwhile, the content of soluble sugar in the tea is improved, the phenol-ammonia ratio of the tea is reduced, the astringency is reduced, the tea is fresh and sweet, and the taste quality of the tea is effectively improved; the chitosan oligosaccharide selenium coordination compound is applied to the planting of selenium-enriched tea, so that photosynthesis of tea trees is enhanced, and the resistance regulating capability of the tea trees to abiotic stress is improved.

Description

Chitosan oligosaccharide selenium coordination compound and preparation method and application thereof

Technical Field

The invention belongs to the technical field of selenium-enriched tea planting, and particularly relates to a chitosan oligosaccharide selenium coordination compound, a preparation method and application thereof.

Background

Selenium (Se) is a non-metallic trace element essential to the human body, and it can improve the immunity of the body and prevent the occurrence of various diseases. Se also plays an important role as a protective agent for abiotic stress of plants, including heavy metals, low temperature, flooding, drought and nutrient deficiency. Mainly shows the antagonism to heavy metals, the detoxification of harmful organic compounds, such as proline, free amino acids, improved antioxidant defense system (superoxide dismutase (SOD), peroxidase (POD), glutathione Peroxidase (GPX), catalase (CAT), etc.). Active oxygen and nitrogen species are detoxified by enhancing photosynthetic activity, chlorophyll content, regulating transpiration rate, and altering plant nutrient metabolism, protecting films and important biomolecules from physiological stress, thereby improving plant growth and biomass production.

Chitosan oligosaccharide (Chitosan Oligosaccharide), also known as chitooligosaccharide, is known under the academic name beta-1, 4-oligosaccharide-glucosamine, and is called "sixth element of life" as a cationic automatic animal fiber substance with free amino basic groups exclusively in the world. Because of their unique physicochemical properties, chitosan oligosaccharides have been widely used in agricultural production as an effective plant immunostimulant, plant growth regulator, stress tolerance inducer, yield and quality promoter, and fruit preservative. The raw materials and methods of chitosan oligosaccharide production are all environmentally friendly, and by adding a strong plant defense induction effect, chitosan oligosaccharide becomes a promising option for sustainable agriculture.

Tea tree is an ideal carrier of selenium, has strong selenium-rich capability, and can convert inorganic selenium into organic selenium beneficial to human body. Natural selenium-rich tea is mainly produced in areas with high selenium content in soil, while in areas with low selenium, selenium enrichment can be achieved by applying selenium-containing fertilizer or spraying selenate or selenite on the surface of tea leaves. At present, in the field of selenium-enriched tea planting, the planting method of selenium-enriched tea described in patent CN 103798015B is mainly characterized in that a fermented organic selenium fertilizer is applied in the tea tree fertilization process, the fermentation condition of the organic selenium fertilizer is complex, the fermentation time is long, pathogenic fungi which are unfavorable for the growth of tea trees are easy to breed in the fermentation process, and a series of consequences such as tea tree contamination, tea yield reduction, tea quality reduction and the like can be caused. Patent CN 105145264B discloses a planting method of selenium-enriched tea, mainly by means of a slow-release fertilizer application device, fermented organic fertilizer is applied, and selenium element is from selenium ore, selenium yeast and sodium selenite. The fertilizer application mode does not necessarily ensure that the tea absorbs selenium and converts selenium, but rather, a large amount of selenium element is in direct contact with soil, so that the soil selenium pollution is easy to cause. Patent CN 105294251A discloses application of chitosan functionalized nano-selenium compound bacterial enzyme system in tea planting, selenium is added in a nano-selenium form, and particularly when the selenium is combined with bacterial enzyme complex, the selenium is easy to react with the bacterial enzyme complex, the biological utilization rate is low, and the biological titer of the bacterial enzyme complex is also reduced.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a chitosan oligosaccharide selenium coordination compound and a preparation method and application thereof.

To achieve the above object, the solution of the present invention is:

the invention provides a preparation method of a chitosan oligosaccharide selenium coordination compound, which comprises the following steps:

(1) Dissolving a certain amount of chitosan oligosaccharide in water, stirring and dissolving, and treating by an ultrafiltration membrane to obtain a chitosan oligosaccharide solution with specific molecular weight;

(2) Mixing chitosan oligosaccharide solution and glucosamine solution according to the volume ratio of 1: (1-2) mixing, adding water with the volume of 20-40 times of that of the glucosamine solution, and stirring until the glucosamine solution is dissolved;

(3) Dropwise adding inorganic selenium solution at a constant rate, keeping the temperature at 90-100 ℃, and continuously stirring until the reaction solution turns from colorless to red and does not change any more;

(4) Dialyzing the reaction solution to obtain a dialysate;

(5) Concentrating and drying the dialyzate to obtain the reddish brown chitosan oligosaccharide selenium coordination compound.

As a preferred embodiment of the invention, in step (1), the ultrafiltration membrane has a pore size of 1000-3000Da molecular weight and the concentration of the chitosan oligosaccharide solution is 0.1-0.6wt%.

As a preferred embodiment of the present invention, in the step (2), the concentration of the glucosamine solution is 50-70mmol/L.

In step (3), the inorganic selenium is one or more selected from the group consisting of selenium dioxide, selenic acid, and sodium selenite.

As a preferred embodiment of the invention, in the step (3), the titration time of the inorganic selenium solution is 0.5-1h, the volume ratio of the added inorganic selenium solution to the glucosamine solution is 1 (1-2), and the concentration of the inorganic selenium solution is 10-30mmol/L.

The second purpose is to provide a chitosan oligosaccharide selenium coordination compound, which is obtained by the preparation method.

Thirdly, the invention provides application of the chitosan oligosaccharide selenium coordination compound in improving the yield and quality of selenium-enriched tea.

As a preferred embodiment of the invention, the application of the chitosan oligosaccharide selenium coordination compound in improving the yield and quality of selenium-enriched tea comprises the following steps:

(1) And (3) plant growth period management: after one month after the tea seedlings are transplanted, ditching and applying a fermentation organic fertilizer to the roots of the tea seedlings; after three months after transplanting, spraying foliar nutrient solution on the tea seedlings;

(2) Management before picking tea leaves: spraying foliar nutrient solution to tea seedlings within 2-5 weeks before picking tea leaves; when spraying, the sun-back surface of the tea is selected as a spraying object, and the spray is applied to the wet tea without dripping water; picking after 1 month of application, and making into tea.

Further, in the step (1) and the step (2), the specific formula of the foliar nutrient solution is that 5-7g of chitosan oligosaccharide selenium coordination compound, 30-40g of water-soluble chitosan, 0.1-0.2g of ferrous sulfate, 0.5-1.0mg of zinc sulfate, 1-2mg of magnesium sulfate, 0.2-0.3mg of manganese sulfate, 2-3g of ammonium nitrate, 3-4g of potassium nitrate and 0.5-1.5g of monoammonium phosphate are dissolved in 1L of water.

By adopting the scheme, the invention has the beneficial effects that:

the first, the invention provides a preparation method of a green chitosan oligosaccharide selenium compound, which has definite ingredients, simple preparation raw materials, wide sources and low cost, and the prepared chitosan oligosaccharide selenium compound has high selenium element content and good biocompatibility, and the chitosan oligosaccharide selenium compound is applied to the planting of high-quality selenium-enriched tea leaves, so that the photosynthesis of tea trees is enhanced, the resistance regulation capability of the tea trees to abiotic stress is improved, the growth vigor of the tea trees is improved, and the preparation method is mainly used for improving the yield, the content level of main nutrient substances and the oxidation resistance of the tea leaves.

Secondly, the chitosan oligosaccharide selenium coordination compound is used for planting the selenium-rich tea, the selenium content of the obtained selenium-rich tea is stable, the selenium content of the selenium-rich tea reaches the national standard (NY/T600-2002), the organic selenium content is more than 80%, and the selenium supplementing requirement of a human body is met.

Thirdly, the chitosan oligosaccharide selenium coordination compound is applied to the planting of the selenium-enriched tea, so that the content of soluble sugar is increased, the phenol-ammonia ratio of the tea is reduced, and the tea soup is delicious, refreshing and sweet, thereby effectively improving the quality of the tea.

Drawings

FIG. 1 is a scanning electron microscope image of a chitosan oligosaccharide selenium complex compound according to an embodiment of the present invention.

FIG. 2 is a graph showing the energy spectrum of a chitosan oligosaccharide selenium complex compound according to an embodiment of the present invention.

FIG. 3 shows the growth of tea plants grown in an example of the present invention.

Detailed Description

The invention provides a chitosan oligosaccharide selenium coordination compound and a preparation method and application thereof.

< preparation method of Chitosan oligosaccharide selenium Complex Compound >

The preparation method of the chitosan oligosaccharide selenium coordination compound comprises the following steps:

(1) Dissolving a certain amount of chitosan oligosaccharide in water, stirring and fully dissolving, and treating by an ultrafiltration membrane to obtain a chitosan oligosaccharide solution with specific molecular weight;

(2) Mixing chitosan oligosaccharide solution and glucosamine solution according to the volume ratio (v/v) of 1: (1-2) mixing, adding water with the volume of 20-40 times of that of the glucosamine solution, and stirring until the glucosamine solution is fully dissolved;

(4) Dialyzing the reaction solution in a dialysis bag to remove unreacted micromolecular substances, and collecting the dialyzate;

Wherein in step (1), the pore size of the ultrafiltration membrane may be in the range of 1000-3000Da, preferably 2000 Da; the concentration of the chitosan oligosaccharide solution may be 0.1 to 0.6wt%, preferably 0.1wt%.

In step (2), the concentration of the glucosamine solution may be 50-70mmol/L, preferably 70mmol/L.

In the step (3), the inorganic selenium is selected from one or at least two of selenium dioxide, selenic acid and sodium selenite.

In step (3), the titration time of the inorganic selenium solution may be 0.5-1h, preferably 0.5h; the volume ratio of the added inorganic selenium solution to the glucosamine solution is 1 (1-2), and the concentration of the inorganic selenium solution can be 10-30mmol/L, preferably 30mmol/L.

< Chitosan oligosaccharide selenium Complex >

The chitosan oligosaccharide selenium coordination compound is obtained by the preparation method. The product containing the chitosan oligosaccharide selenium coordination compound is a biological organic selenium fertilizer or a biological pesticide; more preferably, the product is a foliar fertilizer.

< application of Chitosan oligosaccharide selenium Complex Compound >

The chitosan oligosaccharide selenium coordination compound is applied to improving the yield and quality of selenium-enriched tea. The method is mainly used for preparing one or more of products for promoting plants to absorb selenium, improving plant yield, regulating plant growth, preventing and controlling plant diseases and insect pests and improving plant disease resistance.

Wherein the tea quality is the nutrient content of tea or the oxidation resistance of tea.

Specifically, the application of the chitosan oligosaccharide selenium coordination compound in improving the yield and the quality of tea leaves comprises the following steps:

(2) Management before picking tea leaves: spraying foliar nutrient solution to tea seedlings within 2-5 weeks before picking tea leaves; when spraying, preparing 1 part of foliar nutrient solution and 10-20 parts of water into a spraying nutrient solution, selecting the back-yang surface of tea leaves as a spraying object, and spraying until the tea leaves are wet but not drip water, wherein the application amount is 4 kg/mu; picking after 1 month of application, and making into tea.

Wherein, in the step (1) and the step (2), the specific formula of the foliar nutrient solution is that 5-7g of chitosan oligosaccharide selenium coordination compound, 30-40g of water-soluble chitosan, 0.1-0.2g of ferrous sulfate, 0.5-1.0mg of zinc sulfate, 1-2mg of magnesium sulfate, 0.2-0.3mg of manganese sulfate, 2-3g of ammonium nitrate, 3-4g of potassium nitrate and 0.5-1.5g of monoammonium phosphate are dissolved in 1L of water.

In practice, the specific application mode of the foliar nutrient solution is that 1 part of foliar nutrient solution and 10-20 parts of water are prepared into a spraying nutrient solution, the back-yang surface of tea leaves is selected as a spraying object during spraying, and the spraying is carried out until the tea leaves are wet but not drip water, and the application amount is 4 kg/mu.

The present invention will be described in further detail with reference to preferred embodiments for the purpose of making the objects, technical solutions and advantages of the present invention more apparent. It should be noted, however, that numerous details are set forth in the description merely to provide a thorough understanding of one or more aspects of the invention, and that aspects of the invention may be practiced without these specific details.

The invention is further illustrated below with reference to specific examples.

Examples:

the tea garden developed by Shanghai Jinshan mountain area Fengjing town is selected, the gentle slope land with the gradient less than or equal to 20 degrees is selected, the pH value of soil is most suitable for 4.5-5.5, and the rainwater is abundant.

(1) Dissolving a certain amount of chitosan oligosaccharide in water, stirring and fully dissolving, and treating by an ultrafiltration membrane with a molecular weight of 2000Da to obtain a chitosan oligosaccharide solution with a specific molecular weight of 0.1wt%.

(2) The chitosan oligosaccharide solution and 70mmol/L glucosamine solution are mixed according to the volume ratio (v/v) of 1:1, adding water with the volume of 20 times of that of the glucosamine solution, and stirring until the glucosamine solution is fully dissolved.

(3) 30mmol/L selenious acid solution is dripped at a constant rate, the temperature is kept at 90 ℃, and stirring is continued until the reaction liquid changes from colorless to red and no change occurs.

Wherein, in the step (3), the titration time of the selenious acid solution is 0.5h.

The application of the chitosan oligosaccharide selenium coordination compound in improving the yield and the quality of the selenium-enriched tea comprises the following steps:

(1) And (3) plant growth period management: after one month after the tea seedlings are transplanted, ditching and applying a fermentation organic fertilizer to the roots of the tea seedlings; and after three months after transplanting, spraying foliar nutrient solution on the tea seedlings.

(2) Management before picking tea leaves: spraying foliar nutrient solution to tea seedlings within 5 weeks before picking tea leaves; when spraying, the sun-back surface of the tea is selected as a spraying object, and the spray is applied to the wet tea without dripping water. Picking after 1 month of application, and making into tea.

Wherein in the step (1) and the step (2), the specific formula of the foliar nutrient solution is that 5g of chitosan oligosaccharide selenium coordination compound, 30g of water-soluble chitosan, 0.1g of ferrous sulfate, 0.5mg of zinc sulfate, 1mg of magnesium sulfate, 0.2mg of manganese sulfate, 2g of ammonium nitrate, 3g of potassium nitrate and 0.5g of ammonium dihydrogen phosphate are dissolved in 1L of water.

The results of the treatment performed in the test area on day 4 and day 19 are shown in FIG. 3. As can be seen from fig. 3, the comparison between the control group (the foliar nutrient solution is replaced by the equal volume of clear water) and the treatment group (the experimental group example) shows that the bud heads of the tea tree in the control group are sparse and the leaves are thin; the treated tea tree has dense bud heads, thick leaves, wide leaves, better growth, advanced germination, bright leaves and other obvious advantages. As shown in Table 1, the photosynthetic pigment content of the treated group was increased by 26.93% and the bud weight was increased by 12.28% as compared with the control group, and the yield increase was realized by the planting method provided above.

Further, as shown in table 1, compared with the control group, the treatment group has reduced Malondialdehyde (MDA) which is a marker of membrane lipid peroxidation by 10.66%, and increased content of antioxidant substances such as ascorbic acid (ASA), glutathione (GSH), catalase (CAT), glutathione Peroxidase (GPX), peroxidase (POD), superoxide dismutase (SOD) and enzyme activity of antioxidant enzyme, thus enhancing regulation of ASA-GSH cycle of tea tree and enhancing resistance of the tea tree to abiotic stress oxidative stress. In addition, the active center of the glutathione peroxidase is selenium cysteine, the activity of the glutathione peroxidase can reflect the selenium level of the organism, and compared treatment group results show that the activity of the glutathione peroxidase is greatly improved, and the organic selenium level in the tea is greatly improved.

TABLE 1 detection results of growth physiological index of selenium-enriched spring tea

And (3) withering the tea leaves and naturally airing to prepare the white tea. As can be seen from table 2, comparing the quality indexes of the white tea samples of the control group and the treatment group, it is evident that the contents of the soluble sugar, tea polyphenol, theanine, ester catechin and non-ester catechin of the treatment group are higher than those of the control group, and the alkaloid components with strong bitter taste and astringency are also significantly improved. The polyphenol oxidase (PPO) is used as an important endogenous enzyme for the quality formation of white tea, and the improvement of the enzyme activity of the polyphenol oxidase (PPO) plays a promoting role in improving the color, the aroma and the taste of tea soup.

Table 2 quality test results of selenium-enriched spring tea

As can be seen from Table 3, the selenium content of the treated group sample is significantly higher than that of the control group sample, the trace element contents such as iron, calcium, magnesium and zinc are also significantly improved, the trace elements are all related to photosynthesis of tea trees, copper is a component of a plurality of oxidases in plants, and superoxide dismutase with coexistence of copper and zinc has the effect of catalyzing superoxide radical disproportionation, so that chloroplasts can be protected from being damaged by the superoxide radical.

TABLE 3 detection results of selenium and microelements of selenium-enriched spring tea

Experimental results show that the spring tea planted by the embodiment not only improves the content of organic selenium, but also is beneficial to improving the photosynthesis capacity of tea trees and improving the yield of tea. Meanwhile, the antioxidant substance content and the antioxidant enzyme activity of the tea tree planted by adopting the embodiment are obviously improved, which indicates that the tolerance of the tea tree to abiotic stress is enhanced. In addition, the content of theanine in tea leaves is obviously improved, the phenol-ammonia ratio of tea trees is reduced, and the content of soluble sugar is improved, so that the tea soup presents fresh and sweet taste.

The previous description of the embodiments is provided to facilitate a person of ordinary skill in the art in order to make and use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above-described embodiments. Those skilled in the art will appreciate that, in light of the principles of the present invention, improvements and modifications can be made without departing from the scope of the invention.

Claims

1. A preparation method of a chitosan oligosaccharide selenium coordination compound is characterized by comprising the following steps: the method comprises the following steps:

(1) Dissolving chitosan oligosaccharide in water, stirring and dissolving, and treating by an ultrafiltration membrane to obtain a chitosan oligosaccharide solution;

(2) Mixing the chitosan oligosaccharide solution with the glucosamine solution, adding water with the volume of 20-40 times of that of the glucosamine solution, and stirring until the chitosan oligosaccharide solution and the glucosamine solution are dissolved;

(3) Dropwise adding an inorganic selenium solution, keeping the temperature at 90-100 ℃, and continuously stirring until the reaction solution turns from colorless to red and does not change any more;

(4) Dialyzing the reaction liquid to obtain a dialysate;

(5) Concentrating and drying the dialyzate to obtain a reddish brown chitosan oligosaccharide selenium coordination compound;

in the step (1), the pore diameter of the ultrafiltration membrane is 1000-3000Da molecular weight, and the concentration of the chitosan oligosaccharide solution is 0.1-0.6wt%;

in the step (2), the concentration of the glucosamine solution is 50-70mmol/L, and the volume ratio of the chitosan oligosaccharide solution to the glucosamine solution is 1 (1-2);

in the step (3), the inorganic selenium is selected from more than one of selenium dioxide, selenic acid and sodium selenite;

in the step (3), the titration time of the inorganic selenium solution is 0.5-1h, the volume ratio of the added inorganic selenium solution to the glucosamine solution is 1 (1-2), and the concentration of the inorganic selenium solution is 10-30mmol/L.

2. A chitosan oligosaccharide selenium coordination compound, which is characterized in that: which is obtained by the process of claim 1.

3. Use of the chitosan oligosaccharide selenium complex compound according to claim 2 for improving the yield and quality of selenium-enriched tea leaves.

4. A use according to claim 3, characterized in that: the application of the chitosan oligosaccharide selenium coordination compound in improving the yield and the quality of the selenium-enriched tea comprises the following steps:

(2) Management before picking tea leaves: spraying foliar nutrient solution to tea seedlings within 2-5 weeks before picking tea leaves; when spraying, the sun-back surface of the tea is selected as a spraying object, and the spray is applied to the wet tea without dripping water; picking after 1 month of application, and making tea;

in the step (1) and the step (2), the specific formula of the foliar nutrient solution is that 1L of water is dissolved with 5-7g of chitosan oligosaccharide selenium coordination compound, 30-40g of water-soluble chitosan, 0.1-0.2g of ferrous sulfate, 0.5-1.0mg of zinc sulfate, 1-2mg of magnesium sulfate, 0.2-0.3mg of manganese sulfate, 2-3g of ammonium nitrate, 3-4g of potassium nitrate and 0.5-1.5g of monoammonium phosphate.